TRUE VOLCANOES. 431 



between 47 south and 66 north latitude, in a direction 

 from south-east to north-west. 



If we suppose the great gulph of the sea, known under 

 the name of the South Sea, or South Pacific Ocean, to be 

 cosmically bounded by the parallel of Behring's Straits, and 

 that of New Zealand, which is also the parallel of South 

 Chili and North Patagonia, we shall find and this result 

 is very remarkable in the interior of the basin, as well 

 as around it (on its Asiatic and American continental boun- 

 daries), 198, or nearly seven-eighths of the 225 still active 

 volcanoes of the whole earth. The volcanoes nearest the 

 poles are, so far as our present geographical knowledge goes, 

 in the northern hemisphere the volcano Esk, on the small 

 island of Jan Meyen, in lat. 71 1', and west long. 7 30' 30", 

 and in the southern hemisphere Mount Erebus, whose red 

 flames are visible even by day, and which Sir James Ross, 39 

 on his great southern voyage of discovery in 1841, found to 

 be 12,400 feet high, or about 240 feet higher than the Peak 

 of Teneriffe, in lat. 77 33', and long. 166 58' 30" east. 



The great number of volcanoes on the islands and on 

 the shores of continents must have early led to the investi- 

 gation by geologists of the causes of this phenomenon. I 

 have already, in another place (Cosmos, vol. i, p. 242), men- 

 tioned the confused theory of Trogus Pompeius under Augus- 

 tus, who supposed that the sea- water excited the volcanic fire. 

 Chemical and mechanical reasons for this supposed effect of 

 the sea have been adduced to the latest times. The old 

 hypothesis of the sea- water penetrating into the volcanic 

 focus seemed to acquire a firmer foundation at the time of the 

 discovery of the metals of the earth by Davy, but the great 

 discoverer himself soon abandoned the theory to which even 

 Gay-Lussac inclined, 40 in spite of the rare occurrence, or total 

 absence of hydrogen gas. Mechanical, or rather dynamical 

 causes, whether sought for in the contraction of the upper 

 crust of the earth and the rising of continents, or in the 

 locally diminished thickness of the inflexible portion of the 



39 Sir James Ross, Voyage to the Antartic Regions, vol. i, pp. 217, 

 220, and 3C4. 



40 Gay-Lussac, Reflexions sur les Volcans in the Annales dc Chimie ct 

 de Physique, t. xxii, 1823, p. 429 ; see above, p. 169 ; Arago, (Euvret 

 completes, t. iii, p. 47. 



